Cancer was responsible for about 13% of all human deaths in 2007. Although there are several therapies for cancer, there remains a need for therapies that effectively kill the tumor cells while not harming non-cancerous cells.
In order to minimize the side effects of conventional cancer therapies, including surgery, radiation and chemotherapy, molecular targeted cancer therapies have been developed. Among the existing targeted therapies, monoclonal antibodies (MAb) therapy have the longest history, and to date, over 25 therapeutic MAbs have been approved by the Food and Drug Administration (FDA) (Waldmann, Nat Med 9:269-277, 2003); Reichert et al., Nat Biotechnol 23:1073-1078, 2005). Effective MAb therapy traditionally depends on three mechanisms: antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and receptor blockade and requires multiple high doses of the MAb. MAbs have also been used at lower doses as vectors to deliver therapies such as radionuclides (Goldenberg et al., J Clin Oncol 24, 823-834, 2006) or chemical or biological toxins (Pastan et al., Nat Rev Cancer 6:559-565, 2006). Ultimately, however, dose limiting toxicity relates to the biodistribution and catabolism of the antibody conjugates.
Conventional photodynamic therapy (PDT), which combines a photosensitizing agent with the physical energy of non-ionizing light to kill cells, has been less commonly employed for cancer therapy because the current non-targeted photosensitizers are also taken up in normal tissues, thus, causing serious side effects, although the excitation light itself is harmless in the near infrared (NIR) range (FIG. 9).